1. Field of the Invention
The present invention relates to methods and apparatus for forming metal and metal alloy casings in well bores.
2. Description of the Prior Art
In the drilling and completion of well bores, hydraulic cement compositions are commonly used for cementing strings of metal pipe such as casings or liners in well bores. In such cementing operations, referred to in the art as primary cementing, a hydraulic cement composition is pumped into the annular space between the walls of a well bore and the exterior surfaces of a pipe string disposed therein. The cement composition is permitted to set in the annular space thereby forming an annular sheath of hardened substantially impermeable cement therein. The cement sheath physically supports and positions the pipe string in the well bore and bonds the exterior surfaces of the pipe string to the walls of the well bore whereby the undesirable migration of fluids between zones or formations penetrated by the well bore is prevented. While such primary cementing operations have been successful, they are generally time consuming and expensive.
Thus, there are continuing needs for improved methods of sealing well bores which are less time consuming and less expensive than the current practice of running casing and performing primary cementing operations.
The present invention provides methods and apparatus for forming metal casings in well bores which meet the needs described above and overcome the deficiencies of the prior art. The methods of this invention for forming metal casings in well bores are basically comprised of the following steps. A fluid suspension of a particulate metal or metal alloy having known melting and solidification temperatures is provided. The fluid suspension is pumped into a drill string or work string disposed within the well bore having a casing forming tool connected thereto. The casing forming tool includes an internal passageway sealingly communicated with the drill or work string and with a plurality of radial openings in the tool positioned around the periphery thereof. The fluid suspension of the particulate metal or metal alloy flows from the drill string or work string, through the casing forming tool and into contact with the walls of the well bore. The casing forming tool also includes an internal heater for heating the fluid suspension and melting the particulate metal or metal alloy as it flows through the tool. An internal rotating impeller for imparting centrifugal force to the fluid suspension as it flows through the tool is also disposed within the tool so that the melted particulate metal or metal alloy in the fluid suspension is deposited on the walls of the well bore and forms a casing which solidifies on the walls of the well bore. A sizing mandrel is attached to the casing forming tool for sizing the internal casing diameter of the solidifying metal or metal alloy. The pipe string and the casing forming tool are moved through the well bore while the fluid suspension is pumped through the pipe string and the casing forming tool at rates of movement and pumping whereby a solidified casing having a desired internal diameter is formed in the well bore.
The metal or metal alloy having known melting and solidification temperatures utilized depends on the well bore temperature. That is, a metal or metal alloy is utilized which has melting and solidifying temperatures above the highest temperature to be encountered in the well bore. The particular metal or metal alloy utilized is generally comprised of two or more metals selected from the group consisting of bismuth, tin, lead, antimony, mercury, cadmium silver, gallium, zinc, aluminum, copper, silicon, tellurium and indium. Non-alloyed metals such as tin alone, bismuth alone and lead alone can also be used.